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Message-ID: <20121220155147.GA2048@sgi.com> Date: Thu, 20 Dec 2012 09:51:47 -0600 From: Cliff Wickman <cpw@....com> To: HATAYAMA Daisuke <d.hatayama@...fujitsu.com> Cc: kexec@...ts.infradead.org, ptesarik@...e.cz, linux-kernel@...r.kernel.org, kumagai-atsushi@....nes.nec.co.jp, vgoyal@...hat.com Subject: Re: [PATCH] makedumpfile: request the kernel do page scans On Thu, Dec 20, 2012 at 12:22:14PM +0900, HATAYAMA Daisuke wrote: > From: Cliff Wickman <cpw@....com> > Subject: Re: [PATCH] makedumpfile: request the kernel do page scans > Date: Mon, 10 Dec 2012 09:36:14 -0600 > > On Mon, Dec 10, 2012 at 09:59:29AM +0900, HATAYAMA Daisuke wrote: > >> From: Cliff Wickman <cpw@....com> > >> Subject: Re: [PATCH] makedumpfile: request the kernel do page scans > >> Date: Mon, 19 Nov 2012 12:07:10 -0600 > >> > >> > On Fri, Nov 16, 2012 at 03:39:44PM -0500, Vivek Goyal wrote: > >> >> On Thu, Nov 15, 2012 at 04:52:40PM -0600, Cliff Wickman wrote: > > > > Hi Hatayama, > > > > If ioremap/iounmap is the bottleneck then perhaps you could do what > > my patch does: it consolidates all the ranges of physical addresses > > where the boot kernel's page structures reside (see make_kernel_mmap()) > > and passes them to the kernel, which then does a handfull of ioremaps's to > > cover all of them. Then /proc/vmcore could look up the already-mapped > > virtual address. > > (also note a kludge in get_mm_sparsemem() that verifies that each section > > of the mem_map spans contiguous ranges of page structures. I had > > trouble with some sections when I made that assumption) > > > > I'm attaching 3 patches that might be useful in your testing: > > - 121210.proc_vmcore2 my current patch that applies to the released > > makedumpfile 1.5.1 > > - 121207.vmcore_pagescans.sles applies to a 3.0.13 kernel > > - 121207.vmcore_pagescans.rhel applies to a 2.6.32 kernel > > > > I used the same patch set on the benchmark. > > BTW, I have continuously reservation issue, so I think I cannot use > terabyte memory machine at least in this year. > > Also, your patch set is doing ioremap per a chunk of memory map, > i.e. a number of consequtive pages at the same time. On your terabyte > machines, how large they are? We have memory consumption issue on the > 2nd kernel so we must decrease amount of memory used. But looking into > ioremap code quickly, it looks not using 2MB or 1GB pages to > remap. This means more than tera bytes page table is generated. Or > have you probably already investigated this? > > BTW, my idea to solve this issue are two: > > 1) make linear direct mapping for old memory, and acess the old memory > via the linear direct mapping, not by ioremap. > > - adding remap code in vmcore, or passing the regions that need to > be remapped using memmap= kernel option to tell the 2nd kenrel to > map them in addition. Good point. It would take over 30G of memory to map 16TB with 4k pages. I recently tried to dump such a memory and ran out of kernel memory -- no wonder! Do you have a patch for doing a linear direct mapping? Or can you name existing kernel infrastructure to do such mapping? I'm just looking for a jumpstart to enhance the patch. -Cliff > > Or, > > 2) Support 2MB or 1GB pages in ioremap. > > Thanks. > HATAYAMA, Daisuke -- Cliff Wickman SGI cpw@....com (651) 683-3824 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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